1987 Bucking After Ignition Replacement
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Instructor
Joined: Jul 2000
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From: MN
Fish-biting....haven't heard that one before but yes, that is actually a good way to describe it! I'll double (quadruple?) check the connections.
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Instructor
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From: MN
Could a failing coil cause these symptoms? Particularly if the rest of the ignition components are new? I have never replaced the coil and I've had the car 15 years. It may be the original for all I know.
Melting Slicks
Joined: Jun 2013
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It could. After all, the secondary winding in the coil is part of the secondary circuit.
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From: MN
True enough. I hate the "throw parts at the problem" approach but this doesn't fall very neatly into any of the troubleshooting scenarios in the manuals. It certainly won't hurt to renew the coil. I was always under the impression that they were pretty robust and either worked or they didn't, i.e. you'd have problems at idle and all other operating conditions.
I suppose it could be that open vs. closed loop had nothing to do with it but instead it was just heat (resistance) buildup in the coil that was causing it to surface.
I suppose it could be that open vs. closed loop had nothing to do with it but instead it was just heat (resistance) buildup in the coil that was causing it to surface.
Melting Slicks
Joined: Jun 2013
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True enough. I hate the "throw parts at the problem" approach but this doesn't fall very neatly into any of the troubleshooting scenarios in the manuals. It certainly won't hurt to renew the coil. I was always under the impression that they were pretty robust and either worked or they didn't, i.e. you'd have problems at idle and all other operating conditions.
I suppose it could be that open vs. closed loop had nothing to do with it but instead it was just heat (resistance) buildup in the coil that was causing it to surface.
I suppose it could be that open vs. closed loop had nothing to do with it but instead it was just heat (resistance) buildup in the coil that was causing it to surface.
The ECM will retard timing when cold, so as the engine warms up, the timing advances, which could make a problem more noticeable.
Also, Air/Fuel ratio in open loop is richer than in closed loop. So the simple fact of it running slightly leaner can bring out the problem more. A lot of people will shoot for oxygen sensor when a problem arises in closed loop, but that's not the only difference from open loop to closed loop.
A lot of the times, timing and AFR can exaggerate a problem more.
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From: MN
New coil installed but the problem is still there. I actually think now there is a slight miss at idle too. I'll check fuel pressures and timing, although I haven't messed with the position of the distributor in years. Very frustrating!! So much for preventative maintenance! Now I wish I had just left it alone. I suppose it could be a weird coincidence and be something completely unrelated to the work I did over the winter. Ugh. The weather's finally nice and I just want to drive the damn thing!!
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From: MN
Fuel pressure checks about 46 with the key on before starting. About 40 at idle. When revving, it hangs right at 38 regardless of engine speed. After shutoff, goes back to about 48. When I do rev it to the point where it's missing, the pressure gauge will occasionally spike from 38 to the mid 40s. Neither of the closest auto parts joints have a timing light available for rent so I haven't gotten that checked yet.
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From: MN
Haven't checked the O2 sensor yet, no. Just went for a quick drive and I'm letting it cool down now. Overall drives great. Miss seems to be very dependent on load. Going up even a slight grade, no problem. Keep engine speed the same after the road levels out (virtually no load) and it happens. I think that's why I can get it to happen when sitting in the garage. After she cools down, I'll take a peek at the O2 sensor. Just seems strange the sensor would get fouled or otherwise fail while sitting over the winter.
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From: MN
Oh, and yes I do have the FSM...and the Haynes for good measure. A lot of the things they say to check are the brand new parts I installed. Which I suppose should be suspect given that's what I've been messing with. Short of buying another set of plugs, wires, cap, etc., I'm not sure how to diagnose those components. I've looked for any arcing but found none. I can pull the cap off again and look for any signs of arcing damage in there. When I swapped out the coil, I did notice some soot on the tip of that piece with the spring (not sure what it's called) where it contacts the rotor. I thought that was odd given all that stuff is new.
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From: MN
Got the cap off and there is soot around the center electrode of the rotor. I'm thinking this is pointing to high resistance between that point and somewhere downstream of that?? I don't remember seeing any soot on the old rotor and that was 15+ years old. There are arcing patterns on the contacts inside the cap but they look clean with no evidence of soot. Bad rotor??? I don't have a multimeter at the moment.
Melting Slicks
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Got the cap off and there is soot around the center electrode of the rotor. I'm thinking this is pointing to high resistance between that point and somewhere downstream of that?? I don't remember seeing any soot on the old rotor and that was 15+ years old. There are arcing patterns on the contacts inside the cap but they look clean with no evidence of soot. Bad rotor??? I don't have a multimeter at the moment.
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From: MN
I finally got around to working on the car again. Checked the resistance on all the plug wires. The highest was 20k ohms and those were the longer ones. Pulled all the plugs and they looked fine. Gaps are correct at .035. All wire connections are secure at the plugs and the cap. Problem is still there; still no codes. The thing runs absolutely great outside of that narrow band of parameters. I'm really stumped on this one. Getting close to taking it to a professional but that always makes me cringe a bit.
Melting Slicks
Joined: Jun 2013
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I finally got around to working on the car again. Checked the resistance on all the plug wires. The highest was 20k ohms and those were the longer ones. Pulled all the plugs and they looked fine. Gaps are correct at .035. All wire connections are secure at the plugs and the cap. Problem is still there; still no codes. The thing runs absolutely great outside of that narrow band of parameters. I'm really stumped on this one. Getting close to taking it to a professional but that always makes me cringe a bit.
Pro
Joined: Aug 2011
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From: Allentown Pa
Did you have the chance to check your EGR valve as suggested earlier? I had similar issues as you currently have...and replaced replaced the parts that you did. Plugged the line to the EGR and the stumble went away. Never got a code either. I have a new EGR waiting to go in.
Racer
Joined: Nov 2008
Posts: 321
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From: Auburndale FL
I would go with this one, check all the connectors at the distro and make sure they are "snapped" on, sometimes they seat hard but don't snap on to the top of the connector.
Also check you fuel pressure regulator vacuum connector perhaps is has developed a leak, since it is close to the distro.
Best of luck....
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From: MN
I've noticed that there are two different AC Delco rotors listed for this engine (D468 and D448X). The D448X is what came in my "tune up kit" from MidAmerica and is white in color with phillips head attachment screws. The D468 is black and has hex screws. Beyond that, the D448X is about $5 vs. around $13 for the D468. Is there a functional difference between these two? I know the rotor I took out of the car had hex screws and was blue in color. I'm tempted to get the D468 and see if that makes any difference. I've searched the interwebs trying to find any comparisons but didn't have much luck.